Cold-formable metal reinforced laminate comprising a polyvinyl halide sheet bonded to a gum plastic sheet

ABSTRACT

COMPOSITES WHICH UTILIZE AN INTERLAYER OF METAL BETWEEN A SHEET OF GRAFT COPOLYMER OF MONOVINYL AROMATIC COMPOUND ON AN ELASTOMER AND A SHEET OF PLASTICIZED VINYL HALIDE POLYMER. THE COMPOSITES DISPLAY IMPROVED HEAT RESISTANCE AND CAN BE COLD-FORMED.

June 22, 1971 s o 3,585,594

' COLD-FORMABLE METAL REINFORCED LAMINATE COMPRISING A POLYVINYL HALIDESHEET BONDED TO A GUM PLASTIC SHEET Filed June 10, 1969 |5 H IGH- IM AEfPOLYSHRENE OR ABS TYPE PLASTIC .7 H V, V A

INVENTOR THOMAS J. STOLKI JOHN W. KLOOSTER,

BY ARTHUR E. HOFFMAN,

RUSSELL H. SCHLATTMAN AT I'ORNI, YS

United States Patent US. Cl. 161-39 6 Claims ABSTRACT OF THE DISCLOSUREComposite-s which utilize an interlayer of metal between a sheet ofgraft copolymer of monovinyl aromatic compound on an elastomer and asheet of plasticized vinyl halide polymer. The composites displayimproved heat resistance and can be cold-formed.

BACKGROUND In the art of plastics, there has been a long felt need forsheet-like composites which are both cold-formable and heat resistant inthe manner of conventionally formed or worked sheet metal. As usedthroughout this document, the terms cold-formable, cold-formed, and/orcoldforming, have reference to the fact that a composite can beconformed to a predetermined shape upon the application to at least oneface thereof of sufiicient pressure to bend the starting compositeformed into the desired predetermined shape under substantially roomtemperature conditions without substantially altering the structure ofthe composite or deteriorating its inherent physical and chemicalproperties. Similarly, as used throughout this document, the terms heatresistant and/or heat resistance have reference to the fact that acomposite has the capacity to resist deformation at elevatedtemperatures (e.g. at temperatures of about 200 F. or even higher).Heretofore, prior art plastic composites generally have not beencold-formable and/or heat resistant for a number of reasons.

For one reason, prior art composites especially those containing glassfibers have tended to crack or become embrittled upon being cold-formedand thereby tend to loose their structural integrity and/or physicalstrength characteristics.

For another reason, prior art composites were often so expensive andcostly as to be completely non-competitive for applications involvingthe use of sheet metal. Frequently, in the art of plastics and plasticcomposites, it has been easier from a processing standpoint and from astarting material standpoint to employ heated molding procedures andgluing procedures to fabricate plastic articles of manufacture ratherthan to employ cold-forming techniques.

There has now been discovered, however, a sheet-like composite utilizingtwo sheets of plastic material, each of different composition, which arelaminated together through an interlayer of metal. The product compositehas generally unexpected and superior cold formability and heatresistance properties. The discovery also includes methods for makingsuch composites.

SUMMARY This invention is directed to sheet-like composites which areadapted to be cold formed and which are heat resistant. These compositescharacteristically utilize two different plastic layers laminatedtogether through a metallic interlayer.

A first layer of such a composite of this invention comprises at leastone interpolymer having a superstrate composed of from about 50 to 98weight percent of chemical- 3,586,594 Patented June 22,, 1971 "ice 1ycombined monovinyl aromatic compound and from about 0 to 48 weightpercent of chemically combined other monomer polymerizable therewithgrafted upon a substrate composed of from 2 to 50 weight percent (allbased on 100 weight percent interpolymer) of an elastome'r having aglass phase transition temperature below about 0 C. and a Youngs Modulusof less than about 40,000 p.s.i Such first layer is furthercharacterized by having:

(A) A transverse average thickness of from about 0.007 to 0.25 inch.

(B) A modulus of elasticity of from about 200,000 to 600,000 p.s.i. at73 F., (determined, for example, using ASTM procedure D-882-61-T forrigid and semi-rigid film and sheeting), and

(C) A tensile elongation to fail of at least about 5 percent at 73 F Asecond layer of such a composite comprises on a 100 weight percent basisfrom about 5 to 70 weight percent of generally continuous, generallyelongated metal portions with open spaces defined therebetween. At leastabout weight percent of said metal portions have a maximum length tominimum width ratios of at least about 10 /1 (in a 6.0 inch squaresample of said second layer). This said second layer has a transverseaverage thickness ranging from about 2 to 85 percent of the totaltransverse average thickness of said composite.

A third layer of such composite comprises from about 60 to 98 weightpercent of at least one vinyl halide poly mer and from about 2 to 40weight percent (on a 100 weight percent basis) of at least oneplasticizer therefor. This said third layer is further characterized byhaving:

(A) A transverse average thickness of from about 0.007 to 0.25 inch.

(B) A modulus of elasticity ranging from about 800 to 4000 p.s.i. at 73F. (determined, for example, using ASTM procedure D8826 lT for flexiblesheet and film), and

(C) A tensile elongation to fail of at least about 25 percent at 73 F.

The said second layer is positioned between said first layer and saidthird layer and is substantially completely enclosed thereby. Said firstlayer and said third layer are directly bonded to one another atsubstantially all places of interfacial contact therebetween throughsaid second layers open spaces.

This invention is also directed to methods for making such composites,and to the cold-formed article-s of manufacture made from suchcomposites.

For purposes of this invention, the term sheeet-like has reference tosheets, films, tubes, extrusion profiles, discs, cons and the like, allgenerally having wall thicknesses corresponding to the thickness of thematrix layer. Those skilled in the art will appreciate that undercertain circumstances, three dimensional sheet-like composites of theinvention may, without departing from the spirit and scope of thisinvention, in effect be filled with some material. In general, asheet-like composite of the invention is self-supporting, that is, itexists in air at room conditions without the need for a separate solidsupporting member in face to-face engagement therewith in order tomaintain the structural integrity thereof withou composite deterioration(as through splitting, cracking, or the like.

For purposes of this invention, tensile modulus of elasticity, tensileelongation to fail, flexibility, and the like, are each convenientlymeasured (using ASTM Test Procedures or equivalent).

For purposes of this invention, the term layer has generic reference tosheets, films, and the like.

Starting materialsfirst layer In general, the first layer can compriseany interpolymer system having characteristics as above indicated. Sucha 3 rubber modified interpolymer system of monovinyl aromatic compoundtypically comprises:

(A) A graft copolymer produced by polymerizing monovinyl aromaticcompound in the presence of a preformed elastomer, and mixtures of such;

(B) A graft copolymer produced by polymerizing monovinyl aromaticcompound and at least one other monomer polymerizable therewith in thepresence of a preformed elastomer, and mixtures of such; and/or (C) Amechanical mixture of (A) and/or (B).

As used herein, the term monovinyl aromatic compound has reference tostyrene (preferred); alkyl-substituted styrene, such as ortho-, meta,and para-methyl styrenes, 2,4-dimethylstyrene, para-ethylstyrene,p-t-butyl styrene, alpha-methyl styrene, alpha-methyl-p-rnethylstyrene,or the like; halogen substituted styrenes, such as ortho-, meta-, andpara-chlorostyrcnes, or bromostyrenes, 2,4-dichlorostyrene, or the like;mixed halo-alkyl-s-ubstituted styrenes, such as2-methyl-4-chlorostyrenc, and the like; vinyl naphthalenes; vinylanthracenes; thereof; and the like. The alkyl substituents have lessthan five carbon atoms per molecule, include isopropyl and isobutylgroups.

In general, such an interpolymer system has a number average molecularweight (M ranging from about 20,000 through 120,000 and the ratio ofWeight average molecular Weight (M to number average molecular weight BT/17,, ranging from about 2 through 10.

In general, suitable elastomers for use in this invention can besaturated or unsaturated, and have a glass phase or second ordertransition temperature below about 0 C. (preferably below about 25 C.),as determined, for example, by ASTM Test D-746-52T, and have a YoungsModulus of less than about 40,000 psi. Examples of suitable elastomersinclude unsaturated elastomers such as homopolymers or copolymers ofconjugated alkadienes (such as butadiene or isoprene), where, in suchcopolymers, at least 50 percent thereof is the conjugated alkadiene;ethylene/ propylene copolymers, neoprene, butyl elastomers, and thelike; and saturated elastomers such as polyurethane, silicone rubbers,acrylic rubbers, halogenated polyolefins, and the like.

A preferred class of elastomers for use in this invention are dienepolymer elastomers. Examples of diene polymer elastomers include, forexample, natural rubber having isoprene linkages, polyisoprene,polybutadiene (preferably one produced using a lithium alkyl or Zieglercatalyst), styrene-butadiene copolymer elastomers, butadiene generallyand may acrylonitrile copolymer elastomer, mixtures thereof, and

the like. Such elastomers include homopolymers and interpolymers ofconjugated 1,3-dienes with up to an equal amount by Weight of one ormore copolymerizable monoethylenically unsaturated monomers, such asmonovinyl aromatic compounds; acrylonitrile, methacrylonitrile; alkylacrylates (e.g. methyl acrylate, butyl acrylate, 2-ethy1- hexylacrylate, etc.); the corresponding alkyl methacrylates, acrylamides(e.g. acrylamide, methacrylamide, N- butyl acrylamide, etc.);unsaturated ketones (e.g. vinyl methyl ketone, methyl isopropenylketone, etc.); alphaolefins (e.g. ethylene, propylene, etc.) pyridines;vinyl esters (e.g. vinyl acetate, vinyl stearate, etc.); vinyl andvinylidene halides (e.g. the vinyl and vinylidene chlorides andbromides, etc.) and the like.

A more preferred group of diene polymer elastomers are those consistingessentially of 75.0 and 100.0 percent by weight of butadiene and/0risoprene and up to 25.0 percent by weight of a monomer selected from thegroup consisting of monovinyl aromatic compounds and unsaturatednitriles (e.g. acrylonitrile), or mixtures thereof. Particularlyadvantageous elastomer substrates are butadiene homopolymer or aninterpolymer of 90.0 to 95.0 percent by weight butadiene and 5.0 to 10.0percent by weight of acrylonitrile or styrene.

Another preferred class of rubbers for use in this inmixtures ventionare acrylic rubbers. Such a rubber may be formed from a poly-merizablemonomer mixture containing at least 40 weight percent of at least oneacrylic monomer of the formula:

where R is a radical of the formula:

and p is a positive whole number of from 4 through 12.

Although the rubber may generally contain up to about 2.0 percent byWeight of a crosslinking agent, based on the weight of therubber-forming monomer or monomers, crosslinking may present problems indissolving the rubber in monomers for a graft polymerization reaction(as when one makes an interpolymer system as described in more detailhereinafter). In addition, excessive crosslinking can result in loss ofthe rubbery characteristics. The crosslinking agent can be any of theagents conventionally employed for crosslinking rubbers, e.g. divinylbenzene, diallyl maleate, diallyl furnarate, diallyl adipate, allylacrylate, allyl methacrylate, diacrylates and dimethacrylates ofpolyhydric alcohols, e.g. ethylene glycol dimethacrylate, etc.

One preferred class of monomers for copolymerizing with monovinylaromatic compounds to produce interpolymer systems suitable for use inthis invention as indicated above are alpha-electronegativelysubstituted ethenes. Suitable such monomers are represented by thegeneric formula:

Where X is selected from the group consisting of CN,

-COOR and CONHR R is selected from the group consiting of hydrogen,

( n 2n 1), n 2n) and n zn) 2,

R is selected from the group consisting of hydrogen, and

' m 2m+1)a n is an integer of from 1 through 4, and

m is an integer of from 1 through 8.

Suitable ethene nitrile compounds of Formula 2 are especially preferredand include acrylontrile (preferred), methacrylonitrile,ethacrylonitrile, 2,4 dicyanobutene-l, mixtures thereof, and the like.

Suitable acrylic compounds of Formula 2 are especially preferred andinclude unsaturated acids such as acrylic acid and methacrylic acid;2,4-dicarboxylic acid butene-l, unsaturated esters, such as alkylacrylates (e.g. methyl acrylate, ethyl acrylate, butyl acrylate, octylacrylate, etc.), and alkyl methacrylates (e.g. methyl methacrylate,ethyl methacrylate, butyl methacrylate, octyl methacrylate, etc.);unsaturated amides, such as acrylamide, methacrylamide, N-butylacrylamide, etc.; and the like.

Another preferred class of monomers for copolymerizing with monovinylaromatic compounds as indicated above are conjugated alkadiene monomers.Suitable such monomers include butadiene, 3-methyl-l,3-butadiene, 2-methyl-l,3-butadiene, piperylene chloroprene, mixtures thereof and thelike. Conjugated 1,3-alkadienes are especially preferred.

Another preferred class of monomers for copolymerizing with monovinylaromatic compounds as indicated above are unsaturated esters ofdicarboxylic acids, such as dialkyl maleates, or fumarates, and thelike.

Considered as a whole, other monomer polymerizable with a monovinylaromatic compound is commonly and preferably anethylenically-unsaturated monomer.

Optionally, a polymerization of monovinyl aromatic compound with atleast one other monomer polymerizable therewith may be conducted in thepresence of up to about 2 weight percent (based on total product polymerweight) of a crosslinking agent such as a divinyl aromatic compound,such as divinyl benzene, or the like. Also optionally, such aninterpolymer system may have chemically incorporated thereinto (asthrough polymerization) a small quantity, say, less than about 2 weightpercent (based on total polymer weight) of a chain transfer agent, suchas an unsaturated terpene (like terpinolene), an aliphatic mercaptan, ahalogenated hydrocarbon, an alpha-methylstyrene dimer, or the like.

In any given rubber-modified interpolymer system of monovinyl aromaticcompound as described above, there is preferably from about 55 to 75weight percent monovinyl aromatic compound; about 5 to 45 weight percentother monomer polymerizable therewith, and from about 5 to 40 weightpercent elastomer (same basis). Of course, any given matrix of such asystem is chosen so as to have physical characteristics as aboveindicated.

Preferred rubber modified interpolymer systems of monovinyl aromaticcompounds are graft copolymers of Type B above. More preferred suchgraft copolymers are those of monovinyl aromatic compound, andalpha-electronegatively substituted ethene grafted onto preformedelastomer substrate such as a polybutadiene; in such a polymer system,the amount of monovinyl aromatic of chemically combinedalpha-electro-negatively sub stituted ethene ranges from about 80 to 5percent (preferably from about to 25 weight percent). In addition, theamount of chemically combined conjugated alkadiene monomer typicallyranges up to about 25 weight percent and preferably from about 5 toweight percent. Such a graft copolymer blend usually has a specificviscosity of from about 0.04 to 0.15, preferably about 0.07 to 0.1,measured as a solution of 0.1 percent of the polymer indimethylformamide at C.

Styrene and acrylonitrile are presently particularly preferredsuperstrate monomers. Although the amount of copolymer superstrategrafted onto the rubber substrate may vary from as little as 10 parts byweight per 100 parts of substrate to as much as 250 parts per 100 parts,and even higher, the preferred graft copolymers have asuperstrate-substrate ratio of about 200: 100 and most desirably about30100:100. With graft ratios above 301100, a highly desirable degree of.improvement in various properties generally is obtained.

The interpolymer systems used in this invention may be produced byvarious known polymerization techniques, such as mass, emulsion,suspension and combinations thereof. Whatever polymerization process isemployed, the temperature, pressure and catalyst (if used) should beadjusted to control polymerization so as to obtain the desired productinterpolymer. If so desired, one or more of the monomers may be added inincrements during polymerization for the purposes of controllingviscosity and/or molecular weight and/or composition. Moreover, it maybe desirable to incorporate low boiling organic, inert liquid diluentsduring a mass polymerization reaction to lower the viscosity,particularly when a rubber is employed. Moreover, the catalyst may beadded in increments, or different catalyst may be added at the same timeor at different points during the reaction. For example, when a combinedmass-suspension process is employed, generally oil-soluble catalysts maybe employed; and both low and high temperature catalysts may beadvantageously used in some reactions.

Mechanical blends may be prepared by simple, conventional physicalintermixing of preformed polymers. Conveniently, one uses startingmaterials in a solid, particulate form, and employs such conventionalequipment as a ribbon blender, a Henschel mixer, a Waring Blendor, orthe like.

Graft copolymers may be prepared, for example, by

polymerizing monomers of the interpolymer in the presence of thepreformed elastomer substrate, generally in accordance with conventionalgraft polymerization techniques, involving suspension, emulsion or masspolymerization, or combinations thereof. In such graft polymerizationreactions, the preformed rubber substrate generally is dissolved in themonomers and this admixtur is polymerized to combine chemically or graftat least a portion of the interpolymer upon the rubber substrate.Depending upon the ratio of monomers to rubber substrate andpolymerization conditions, it is possible to produce both the desireddegree of grafting of the interpolymer onto the rubber substrate and thepolymerization of ungrafted interpolymer to provide a portion of thematrix at the same time. A preferred method of preparation involvescarrying out a partial polymerization in a bulk system with the rubberdissolved in a mixture of the ethene monomers and vinyl aromaticmonomers, followed by completion of the polymerization in an aqueoussuspension system.

Blends may be prepared by blending latices of a graft copolymer and aninterpolymer and recovering the polymers from the mixed latices by anysuitable means, e.g. drum-drying, spray-drying, coagulating, etc.Preferably, they are prepared by simply blending a mixture of theinterpolymer and the hydroxylated graft copolymer at an elevatedtemperature for a period of time sufficient to provide an intimatefusion blend of the polymers. Blends of graft copolymer and copolymercan be prepared by simply blending the two polymers together onconventional plastics working equipment, such as rubber mills,screw-extruders, etc.

As suggested above, the rubber modified interpolymer systems used inthis invention containing monovinyl aromatic compound, elastomer, and,optionally, at least one other monomer copolymerizable with suchmonovinyl aromatic compound. In such a system, at least about 2 weightpercent of the elastomer present is graft polymerized as a substrate to(as indicated) a superstrate of monovinyl aromatic compound and(optionally and preferably) other monomer polymerizable therewith.Typically, a small mount of the superstrate interpolymer is not inchemical combination with the rubber substrate because of theless-than-IOO percent grafting efficiency of conventional graftcopolymerization reactions.

The above-described interpolymer systems are generally well known to theprior art and do not constitute part of the present invention. However,they are to be distinguished from prior art polymer systems such asthose of styrene only with no appreciable amounts of elastomer present(sometimes known as homopolystyrene, as opposed to what is known, forexample, as a graft copolym of styrene on a preformed elastomer). Thus,polystyrene characteristically is a brittle plastic which has a lowersoftening temperature, and a lower tensile strength at yield than doessuch a graft copolymer. In addition, homopolystyrene has differentsolubility characteristics and thermal stability characteristics than dosuch graft copolymers. It is the superior combination of propertiesassociated with such graft copolymers which is believed to contribute tomaking them valuable as starting materials in making the surprising andunexpected composites of the present invention.

It will be appreciated that in any given first layer used in thisinvention, minor amounts of additional additives can be present with onesuch rubber modified interpolymer system of monovinyl aromatic compound,such as monovinyl aromatic compound polymer, a copolymer of monovinylaromatic compound and at least one other monomer polymerizabletherewith, an elastomer, and/ or conventional plastic processingadjuvants, organic or inorganic fillers, flame retardants, antioxidants,stabilizers, plasticizers, and the like, assuming, for example, noadverse eifect upon desired physical properties of a first layer (asindicated above). Assuming compatibility with no adverse effect upon thedesired end composite properties of improved cold formability and heatresistance, a given first layer may also contain a minor amount ofanother polymer, such as a polyvinyl chloride, a polycarbonate, apolysulfonate, a polyphenyleneoxide, a polyamide, or the like, dependingupon individual wishes or circumstances, Without departing from thespirit and scope of this invention. Fibrous fillers may be used.Typically, the amount of such an additive is less than about -20 weightpercent of total first layer weight.

Depending on the method of fabricating a sheet-like composite of thepresent invention, a first layer comprising such interpolymer system isconventionally made into sheet or film form by the usual techniquesconventionally employed in the plastics industry to make such plasticmaterials.

Starting materialssecond layer Any metal layer having characteristics asabove-described can be used as an interlayer in practicing thisinvention. Such layers are known to the prior art, and can have avariety of physical forms, as those skilled in the art will appreciate,but always have elongated metal portions.

As used herein, the phrase generally continuous, generally elongatedmetal portions has reference to the fact that in any given metal layeror interlayer the component metal portions thereof are generallycontinuous and unbroken preferably in at least one direction, takengenerally in relation to one face of a first or second layer in a givencomposite, and also such component metal portions are generallyco-extensive with such matrix in such direction. Preferably, suchcomponent metal portions are generally continuous and unbroken in atleast two such directions (more preferably, one such direction being at90 with respect to the first), and also such portions are generallyco-extensive with such first and second layers in such directions. Aninterlayer by itself is self-supporting (that is, it is not composed ofloose, non-interconnected or non-coherent metal portions). The form ofan interlayer is generally unimportant; interlayers may be pleated,knitted, etc. Considered individually, a metal portion of an interlayerneed have no particular cross-sectional configuration or spatialorientation. The spacing between adjacent filaments or metal portions isnot critical, but it is preferred that such be at least sufficient topermit the interpolymer system or systems used in a given instance toflow thereinto during manufacture, for example, by the application ofheat and pressure to exposed, opposed faces of a composite being made.In any given interlayer of a particular composite, the metal portionsare preferably similar in character to one another to enhance uniformityof product characteristics in a finished composite.

Preferably, a given interlayer has the open spaces between such metalportions occurring in a generally regular and recurring pattern. Thephrase generally regular and recurring pattern has reference to the factthat in an interlayer there is a predictable relationship between onerelatively sub-portion thereof and another, as viewed from a facethereof in a macroscopic sense. Such a regular and recurring pattern,and such continuous, elongated metal portions, in an interlayer aredeemed preferable to obtain the cold formability and heat resistanceassociated with composite products of this invention. Examples of twoclasses of metal layers having such a space pattern are woven Wire mesh,and perforated sheet metal (including, generically, both perforated andexpanded metal, and the like). Examples of suitable metals for wovenwire mesh and perforated metal include ferrous metals (iron, steel, andalloys thereof), cuprous metals (copper, brass, and alloys thereof),aluminum and aluminum alloys, titanium, tantalum noble metals, and thelike.

Another class of interlayers useful in the practice of this inventionare those metal layers composed namely 8 of generally randomly arranged,discrete metal filaments which class is sometimes called the metalwools. These filaments may typically have average maximum crosssectionaldimensions ranging from about 5 to '100 mils, and at least about weightpercent (based on total interlayer weight) of all such filaments havelength to width ratios in excess of about 10 1 (preferably 10 /1).

Metal wool is made by shaving thin layers of steel from wire. Typically,the Wire is pulled or drawn past cutting tools or through cutting dieswhich shave off chips or continuous pieces. Steel wire used for themanufacture of steel wool is of generally high tensile strength andtypically contains from about 0.10 to 0.20 percent carbon and from about0.50 to 1 percent manganese (by weight), from about 0.02 to 0.09 percentsulphur, from about 0.05 to 0.10 percent phosphorus and from about 0.001to 0.010 percent silicon. Preferably, such wire used as a startingmaterial displays an ultimate tensile strength of not less than about120,000 pounds per square inch. Metals other than steel are also madeinto wool by the same processes and when so manufactured have the samegeneral physical characteristics. Thus, metal wools are made from suchmetals as copper, lead, aluminum, brass, bronze, Monel metal, andnickel, and the like. Techniques for the manufacture of metal wools arewell known; see, for example, US. Pats. 888,123; 2,256,923; 2,492,019;2,700,811; and 3,050,825.

Commonly, a single filament of a metal wool has three edges, but mayhave four or five, or even more. In a given wool, the strands orfilaments of various types may be mixed. Finest strands or fibers arecommonly no greater than about 0.0005 and the most commonly used type orgrade of wool has fibers varying from about 0.002 to 0.004 inch.Commercially, metal wools are classified into seven or nine distincttypes or grades. A given metal wool is in the form of a pad orcompressed mat of fibers and, as such, is used as an interlayer incomposites of this invention. Although the arrangement of fibers in sucha pad or mat is generally random, the pad or mat may have impartedthereto a cohesive character by various processes in which groups offibers are pulled through or twisted with or otherwise mechanicallyinterlocked loosely with other fibers of the whole mat; however,considering the product mat as a whole, the fibers thereof are randomlyarranged and in a substantially non-woven condition.

Still another class of metal layers which may be used in practicing thisinvention are metal honeycombs, such as those conventionally fabricatedof aluminum, steel, or other metals. Because of structural and rigidityconsiderations, honeycombs under mils in transverse thickness arepreferred for use in this invention.

The strength and stiffness of composites of this invention containinghoneycomb interlayers are influenced by honeycomb cell shape and size,as well as by the gross thickness and mechanical properties thereof.Increasing honeycomb thickness generally results in higher sectionmodulus and increased moment of inertia for a composite as a whole. In aproduct composite, shear load orientation should be considered inrelationship to the particular use to which it is desired to place aproduct composite. In general, shear strength and modulus tend to beanisotropic, being influenced by the cell structure of a given honeycombinterlayer; anisotropic shear property differences are particularlynoticeable in hexagonal cell honeycomb structures. In general, smallerinterlayer cell size and thicker cell walls result in higher compressivestrength; however, density increases. Compressive strength in a productcomposite can be increased by using interlayers having stronger cellwalls (for example, by shifting from 3003 aluminum to 5056 aluminum)without a weight penalty.

Assuming, of course, compatibility, and no adverse effect upon thedesired end composite properties of improved cold formability and heatresistance, a given interlayer may also have as an integral part thereofnonmetallic portions, say up to about Weight percent thereof, orsomewhat more, but preferably not more than about 10 weight percentthereof, and more preferably not more than about 3 weight percentthereof. Such nonmetallic portions may be applied by dipping, spraying,painting, or the like, and may serve, for example, as electricalinsulation, to insulate individual strands one from the other as when anelectric current is to be passed through a product composite, or, foranother example, as an organic or inorganic coating, over the interlayerto enhance, for instance, bonding and adherence between interlayer andmatrix layer. Such non-metallic portions are within the contemplation ofthis invention and are generally obvious to those skilled in the art asit exists today at the time of the present invention.

It will be appreciated that while an interlayer need not be bonded tothe matrix, such is a preferred condition, in general. Observe that aninterlayer is fully enclosed by the matrix layer (except possibly atextreme edge regions) and that the matrix material always extendsbetween the open spaces in an interlayer in a continuous manner.

In general, it is preferred for purposes of the present invention topreform an interlayer before combining it with matrix layers. Theflexibility of the interlayer (that is the ability of an interlayer tobe moved transversely in response to a gross force, as compared to apointed or highly localized force, applied against one face of theinterlayer with the end edges of an interlayer sample being positionedin a generally planar configuration) is preferably at least as great asthe flexibility of the matrix layer similarly measured but without aninterlayer being positioned in such matrix layer.

Starting materialsthird layer Any plasticized vinyl halide polymercomposition having characteristics as above defined can be used incomposites of this invention.

The term vinyl halide polymer as used herein includes a polymer producednot only by polymerizing vinyl chloride monomer to produce polyvinylchloride homopolymer, but also by copolymerizing vinyl chloride monomerwith other ethylenically unsaturated aliphatic monomers having molecularweights generally under about 260 and copolymerizable with vinylchloride to produce polyvinyl chloride include olefins.

Vinyl halide polymers are well known. The vinyl halides which aregenerally suitable for use in the vinyl halide polymer include vinylchloride and vinyl fluoride; vinyl chloride is the preferred monomer andmay be used alone or in combination with vinyl fluoride and/ or otherethylenically unsaturated compound copolymerizable therewith. In thecase of a copolymer with another ethylenically unsaturated compound, theamount of comonomer generally does not exceed about percent of theweight of the resulting vinyl halide polymer, and preferably the amountof the second component is less than about 15 percent of the product.

Ethylenically unsaturated monomers which may be interpolymerized withthe vinyl halides typically have molecular weights under about 260 andinclude vinylidene halides such as vinylidene chloride; vinyl esters ofmonobasic organic acids containing 1-20 carbon atoms such as vinylacetate; acrylic and alpha-alkyl acrylic acids, such as acrylic andmethacrylic acids; the alkyl esters of such acrylic and alkyl-acrylicacids containing 1-20 carbon atoms such as methyl acrylate, ethylacrylate, butyl acrylate, octadecyl acrylate and the correspondingmethyl methacrylate, esters; dialkyl esters of dibasic organic acids inwhich the alkyl groups contain 2-8 carbon atoms, such as dibutylfumarate, diethyl maleate, etc.; amides of acrylic and alkyl-acrylicacids, such as acrylamide, methacrylamide; unsaturated nitriles, such asacrylonitrile, methacrylonitrile, ethacrylonitrile; monovinylidenearomatic hydrocarbons, such as styrene and alpha-alkyl styrenes; dialkylesters of maleic acid, such as dimethyl maleate and the correspondingfumarates; vinyl alkyl ethers and ketones such as vinyl ether, 2-ethylhexyl vinyl ether, benzyl ether, etc. and various other ethylenicallyunsaturated compounds copolymerizable with the vinyl halides. Mixturesof compounds exemplified by the foregoing materials may also be used.

The method used to prepare the vinyl halide resins may be any which iscommonly practiced in the art; the polymerization may be effected enmasse, in solution or with the monomer in aqueous dispersion. From thestandpoint of economics and process control, highly suitable polymersfor the matrix phase can be prepared by a method in which the monomerreactants are suspended in water. Other variations upon thepolymerization method may also be utilized in order to vary theproperties of the product, one example of which is polymerization atrelatively high temperatures which normally produces polymers having thecharacteristics desired in the matrix resin. Highly fluid resins canalso be prepared by utilizing a technique in which the monomer charge ora porton thereof is continuously fed to the reaction vessel, which isbelieved to promote branching.

Two or more vinyl halide polymers may be used in admixture. One suchpolymer may be dispersed as a discontinuous phase in another.

Preferred vinyl halide polymers have chlorine contents ranging fromabout 45.0 to 56.7 and have molecular weights such that a 0.4 weightpercent solution of such polymer in cyclohexanone at 25 C. has aspecific viscosity of from about 0.3 to 0.6. More preferred specificviscosities range from about 0.4 to 0.5. A preferred class of vinylchloride polymer is polyvinyl chloride homopolymer.

Plasticizers for plasticized vinyl halide polymers are well known tothoseof ordinary skill in the art and do not constitute part of thepresent invention. Many suitable plasticizers for such polymers aresold. In general, a plasticizer can be regarded as a material which isadded to a plastic primarily to improve the flexibility of the resultingcomposition. At present, important plasticizers include non-volatileorganic liquids or low melting solids especially the phthalate, adipate,sebacate esters and aryl phosphate esters. Commonly, their molecularweights are under 1000.

Suitable plasticizers include abietic acid derivatives, such ashydroabietyl alcohol and methyl abietate; adipic acid derivatives, suchas dioctyl adipate; azelaic acid derivatives, such as dioctyl azelate;benzoic acid derivatives, such as diethylene glycol benzoate anddipropylene benzoate blend; diphenyl derivatives, such as a chlorinateddiphenyl; citric acid derivatives, such as tri-n-butyl citrate; epoxyderivatives, such as epoxidized octyl talleate; ether derivatives, suchas dibenzyl ether; ethylene diamine derivatives; fumaric acidderivatives, such as dibutyl fumarate; glycol derivatives, such asdiethylene glycol dipelargonate; petroleum derivatives (usually ascoplasticizers); isophthalic acid derivatives, such as diisooctylisophtha-late lauric acid derivatives, ethylene glycol monoethyl etherlaurate; mellitates, such as tri-octyl tri-mellitate; oleic acidderivatives, such as butyl oleate; palmitic acid derivatives; paraflinderivatives, such as chlorinated paraflin (usually as coplasticizers);pelargonic acid derivatives, such as 2-butoxy-ethyl pelargonate;pentaerythritol derivatives such as pentaerythritol fatty acid ester;phenoxy plasticizers; phosphoric acid derivatives, such as tricresylphosphate; phthalic acid derivatives, such as dioctyl phthalate;polyesters; ricinoleic acid derivatives, such as a modified methylrecinoleate; sebacic acid derivatives, such as dioctyl sebacate; stearicacid derivatives, such as butyl acetoxy stearate; oil derivatives, suchas methyl ester of tall oil; and the like.

Minor amounts of conventional additives such as stabilizers, fillers,colorants, processing aids, lubricants, co-

plasticizers, etc. can optionally by incorporated into such vinyl halidepolymer blends as used in this invention, if desired. Thus, for example,among the processing aids and coplasticizers which may be incorporatedinto such blends used in this invention are paraffin; thermoplasticpolymers, such as methyl methacrylate polymers, styreneacrylonitrilecopolymers, styrene-methyl methacrylate copolymers; and the like. Theseblends used in this invention may contain the conventional stabilizers,lubricants and fillers employed in the art for compounding vinylchloride polymer blends, such as antimony oxide, titanium dioxide,calcium carbonate, magnesium silicate, etc., and epoxy components. Theymay also include an inert or surfacertreated inorganic filler, either infinely divided particulate form or in the form of fibers. Particle sizesare typically under about 10 microns. Usually, the total quantity ofsuch additives in a given blend does not exceed about or 8 weightpercent thereof, though somewhat more can be added, assuming no adverseeffect on the above-indicated physical properties of a third layer.

The plastieizer materials can be prepared in the form of mixtures(preferably uniform), or they can be mixed separately with vinyl halidepolymer to produce directly novel heat-fusible, uniform blends ofplasticizer composition and vinyl halide polymer. Typical plasticizeruniform mixtures may be in the form of solids or liquids (solutions ordispersions) while typical uniform blends are in the form ofparticulate, free-flowing solids.

It is convenient, though not necessary, when preparing a blend of aplasticizer composition of this invention with vinyl chloride polymer touse such polymeric materials in the form of particles at least 90 weightpercent of which pass through a 40 mesh USBS sieve. Preblendingtechniques may be used.

The plasticized vinyl halide blends used in this invention can be madeeither by intensive mechanical mixing without fusion in powder form, orby mechanical mixing with heat-fusion followed by dicing (or otherequivalent procedure of particulation).

Suitable mechanical blenders include chain can mixers, ball mills,ribbon blenders, Henschel blenders, and the like, depending uponcircumstances. When using the latter technique, it is convenient andpreferred to prepare a preblend mixture of starting materials bymechanically mixing same, and then to subject such preblend for a shortperiod of time to further mixing at a temperature above the fusion(melting) temperature of the resinous (polymeric) components (startingmaterials) to homogenize same. This homogenizing procedure may beperformed on a 2-roll rubber mill until the polymer fuses and a rollingbank is formed. The roll temperatures are maintained at about 150l70 C.throughout the mixing operation. Alternatively, such a preblend may behomogenized and fused in a Banbury mixer.

When preparing a non-fused powder blend, vinyl chloride polymer andplasticizer composition (plus optional additives) are convenientlymechanically blended in an intensive mixer, such as a Henschel mixer, orthe like. Preferably, the mechanical blends of this invention should bepreferably so intimately admixed as respects the mixture of componentsthereof that the resulting blend when subsequently heat fused staticallyin an air oven demonstrates a substantial freedom from discolorationafter 10 minutes at 190 C. at atmospheric pressure.

A product blend is conveniently made into sheet or film form by theusual techniques conventionally employed in the plastics industry tomake such plastic materials. Depending on the method of fabricating asheet-like composite of the present invention, a third layer ispreferably preformed.

The respective moduli of elasticity associated with the first and withthe third layers used in composites of this invention are conv nientlymeasured using 0.5 inch samples of such respective layers and ASTMprocedure No. D-882-61-T, as summarized by the following Table A:

TABLE A.-CLASSIFICATION OF FILM AND SHEETING [(ASTM D-882-61-T) Modulusof elasticity Semi- .rigid Flexible Rate of grip separation, 20 in./min5' i Determined on in. samples.

Methods of fabrication and use As indicated above, any convenienttechnique for making the composites of this invention can be employed.One method involves the step of first forming a deck of respectiveindividual sheets of preformed first layer, preformed second layer andpreformed third layer, sequentially. Thereafter, one applies to theopposed, exposed faces of the resulting deck elevated temperatures andpressures for a time suificient to cause matrix layers to flow throughopen spaces in the interlayer(s), thereby to consolidate and laminatetogether the first and the third layers to form the desired composites.This method can be continuously practiced.

In making a composite of this invention by lamination involving formingor laying up a deck of alternating sheets (as indicated above), it willgenerally be convenient to employ temperatures in the range of fromabout C. to 250 C., pressures in the range of from about 10 p.s.i. to1000 p.s.i. and times in the range of from about 0.1 second to 30minutes. Pressures, temperatures and times which are greater or smallerthan these specfic values can, of course, be employed without departingfrom the spirit and scope of the invention depending on the needs of anindividual use situation. In general, the lamination conditions are suchthat the matrix sheets are caused to flow through open spaces ininterlayers to form a desired monolithic structure in the composite withsubstantially no open spaces between the former individual layers.

Non-planar composites can be made by conventional techniques as thoseskilled in the art will appreciate. For example, tubes can be made fromflat sheet-like composites by thermoforming the sheets on a form andwelding the seams together as by molding. The tubes can also be producedby continuous extrusion using a tube die and feeding in a preformedcylindrical interlayer to the die. Two dies can be used for continuouslamination or a single die can be used to effectively encapsulate apreformed interlayer. Temperatures generally above the melting point ofthe particular interpolymer system used are preferably employed (e.g.-270 C.). Sometimes roll pressures suificient to cause fusion throughoverlapping faces of matrix material are valuable in formingthree-dimensional shapes. Typical roll pressures range from about 40 to400 pounds per square inch.

To cold-form a sheet-like composite of the present invention, one simplyapplies in a generally continuous manner sutficient pressure to at leastone surface thereof so as to conform the starting composite to apredetermined shape, room temperatures can be employed. In general,conventional cold-forming procedures known to the art can be employedincluding preforming (both by shallow draw stamping and deep drawforming), hydro-forming, drop forging, explosion forming, brake bending,compression molding, and the like.

Articles of manufacture made from the composites of this inventiongenerally comprise shaped bodies formed from a sheet-like composite ofthe invention by applying to such composite (as indicated above(sufficient pressure in a generally continuous manner to convert thestarting composite into the desired shaped body.

DESCRIPTION OF THE DRAWINGS The invention is illustrated by reference tothe attached drawings wherein:

TABLE IIIA.WOVEN WIRE MESH INTERLAYERS Mesh Modulus Tensile Tensilethickelasticity, strength, elongation, Wire ness lbs./in. 2 lbs./in.percent at Type metal used in gauge Mesh Ex. designation (mils) at 73 F.at 73 F. 73 F. mesh (in. size 22 30x10 5 81,500 3 Galvanized steel 01113 20 X10 35, 800 10 Aluminum 010 16 18 25X10 98, 200 40 Stainless Steel009 18 FIG. 1 illustrates a method of making a composite of thisinvention; and

FIG. 2 is an enlarged vertical sectional view of one embodiment of acomposite of this invention.

Referring to FIG. 1, there is seen illustrated a process for making acomposite of this invention. A first layer 15, a second layer 16, and athird layer 17 are laid up sequentially in face-to-face engagement asshown, and the assembly is clamped between the heated jaws 18 of apress. After the first and third layers heat soften, they flow throughopenings in second layer 16 and fuse together at points of interfacialcontact therebetween to form a solid, monolithic structure (see FIG. 2)

Referring to FIG. 2, there is seen a composite of this inventiondesignated in its entirety by the numeral 10. Composite 10 is seen tocomprise a first layer 15, a second layer 16, and a third layer 17, asthese respective layers are herein described and illustrated.

EMBODIMENTS EXAMPLES A THROUGH F Square sheets composed of rubbermodified interpolymer systems of styrene graft copolymers are prepared.The characteristics and composition of each such sheet being as givenbelow in Table II.

TABLE IL-FIRST LAYERS Sheet Modulus thickelasticity,

ness lbs/in. (mils) at 73 F.

Tensile elongation,

percent at Composition (Nos. refer to footnotes) Ex. designation 1 1 milequals 0.001 inch.

2 A graft copolymer of 82 weight percent styrene/acrylonitrile copolymersuperstrate on 18 weight percent butadiene elastomer substrate madeaccording to teachings of U.S. Pat. 3,328,488.

3 A graft copolymer of 92.5 weight percent styrene/acrylonitrilecopolymer superstrate on 7.5 weight percent butadiene elastomersubstrate made according to teachings of U.S. Pat. 3,328,488.

4 A graft copolymer found by analysis to contain about 80 to 85 weightpercent styrene/acrylonitrile copolymer superstrate on about to 20weight percent polyakyl acrylate ester elastomer substrate availablecommercially under the trade designation "Luran-S from Badische Anilin-& Soda-Fabrik, West Germany.

6 A graft copolymer found by analysis to contain styrene/aorylonitrile/methylmethacrylate terpolymer on a polybutadiene elastomer substrateavailable commercially under the trade designation XT from the AmericanCyanamid Company and preparable by the teachings of U.S. Pat. 3,354,238.

A mixture of homopolystyrene and a graft copolymer of styrene polymersuperstrate on a butadiene substrate containing 92% weight percentstyrene and 7% weight percent butadiene, the graft copolymer thereinhaving been prepared by the teachings of U.S. Pat. 3,444,270.

EXAMPLES G THROUGH L Square samples of metal interlayers are prepared,the

characteristics and composition of each being as summarized in TablesIII A, IIIB, IIIC, and III D, below, the di- TABLE =IIIB.PERFORATEDSHEET METAL INTER LAYER Ex. designation I Sheet thickness (mils) 16Modulus elasticity (lbs/in?) at 73 F. l6 10 Tensile strength (lbs/in?)at 73 F. 70 10 Tensile elongation percent at 73 F.

TABLE MIC-METAL WOOL INTERLAYER Ex. designation K Interlayer thickness(in. measured in air under no load) 0.25 Av. max. individual fibercross-sectional dimension (inches) .002 to .004 Type metal Steel 1Apparent length-to-width ratio of more than weight percent In excess 10/1 1 Made from steel wire having an ultimate tensile strength over120,000 pounds per square inch and believed to contain from about 0.10to 0.20 percent carbon, from about 0.50 to 1 1pelrcent manganese, andfrom about 0.02 to 0.09 percent su p iur.

TABLE III'D.HO'NEYCOMB INTERLAYER EXAMPLES M THROUGH Q Square sheetscomposed of plasticized polyvinyl halide are prepared, thecharacteristics and composition of each such sheet being as given belowin Table IV, the dimensions of each such sheet matching those ofExamples A through F (above).

TABLE IVA.THIRD LAYERS Sheet Modulus Tensile Composithickelasticity,elongation, tion (Nos.

' ness lbs/in. percent at refer to Ex. designation (mils) at 73 F. 73 F.footnotes) 30 ca. 2, 800 ca. 300

ca. 2,800 ca. 300

60 ca. 2, 900 ca. 425

60 ca. 4, 000 ca. 235

60 ca. 1, 400 ca. 390 (5) 1 1 mil equals .001 inch.

2 This composition of polyvinyl chloride and plasticizer uses ahomopolymer of vinyl chloride having a specific viscosity incyclohexanone at 20 C. of about 0.48 and has the formulation shown inTable IVB below.

3 This composition uses a homopolymer as in Footnote and has theformulation shown in Table IVB below.

4 This composition uses a homopolymer as in Footnote and has theformulation shown in Table IVB below.

5 This composition uses a copolymer of vinyl chloride and vinyl acetatemade uslng 3 weight percent vinyl acetate monomer and has an inherentviscosity in cyclohexanone at 25 C. of about 1.07 and has theformulation shown in Table IVC below.

TABLE IVB.SHEET COMPOSITION Parts by weight Composi- Composi- Composi-Component tion 2 tion 3 tion 4 Polyvinyl chloride resin l l l 100 100 IDioctyl phthalate plasticizer 30 70 20 Epoxy stabilizer/plasticizer, Pa

plex G-62 from Rohm & Haas"... 3 3 3 Liquid barium/cadmium stabilizer,Mark LL from Argus Chemical Co 2. 75 2. 5 2. 75 Liquid zinc stabilizer,Mark PL from Argus Chemical Co 0. 1 .01 0. 1 Stearic acid lubricant 0. 50. 5 0. 5

73 4 Refer to Table IVA footnotes.

TABLE IVS-SHEET COMPOSITION *Number refers to Table IVA footnotes.

EXAMPLES 1 THROUGH 7 Using the foregoing first layers of Examples Athrough F, the foregoing second layers of Examples G through L and theforegoing third layers of Examples M through Q, composites of theinvention are prepared of the type shown in FIG. 1 of the drawings usingthe procedure illustrated in FIG. 2 thereof. Each composite is exposedto a temperature of about 350 to 400 F. using a pressure of about 500lbs/in. for a time of about minutes before removal from the heated pressand being allowed to cool to room temperature. Constructional detailsare reported in Table V below.

Each such composite product is found to be cold formable and heatresistant.

Those skilled in the art will appreciate that multi-layered compositescan be produced which will contain, for example, at least two of thefirst layers, the second layers, or the third layers beyond compositescontainng only a first layer, a second layer and a thrd layer.

In general, the composites of this invention are characterized bydimensional stability and by substantal freedom from stress crackingover wide environmental temperature ranges.

TABLE Vr-C OMPOSITES 16 weight percent interpolymer) of an elastomerhaving a glass phase transition temperature below about 0 C. and aYoungs Modulus of less than about 40,000 p.s.i., said first layer beingfurther characterized by having:

(1) a transverse average thickness of from about 0.007 to 0.25 inch, (2)a modulus of elasticity of from about 200,000

to 600,000 p.s.i. at 73 F., and 3) a tensile elongation to tail of atleast about 5 percent at 73 F.,

(B) a second layer comprising on a 100 weight percent basis from about 5to weight percent of generally continuous, generally elongated metalportions with open spaces defined therebetween, at least about Weightpercent of said metal portions having a maximum length to minimum widthratios of at least about 10 /1 (in a 6.0 inch square sample of saidsecond layer), and said second layer having a transverse averagethickness ranging from about 2 to 85 percent of the total transverseaverage thickness of said composite, and

(C) a third layer comprising from about 60 to 98 Weight percent of atleast one vinyl halide polymer and from about 2 to 40 weight percent (ona 100 weight percent basis) of at least one plasticizer there for, saidthird layer being further characterized by having:

(1) a transverse average thickness of from about 0.007 to 0.25 inch,

(2) a modulus of elasticity of from about 800 to 4000 p.s.i. at 73 F.,and

(3) a tensile elongation to fail of at least about 5 percent at 73 F.,and

(D) said second layer being positioned between said first layer and saidthird layer and being substantially completely enclosed thereby, andsaid first layer and said third layer being bonded to one another atsubstantially all places of interfacial contact therebetween throughsaid second layers open spaces.

2. The composite of claim 1 wherein the first layer comprises a graftcopolymer of a styrene superstrate grafted on a butadiene substrate.

3. The composite of claim 1 wherein the first layer comprises a graftcopolymer of a styrene/acrylonitrile superstrate grafted on a butadienesubstrate.

4. The composite of claim 1 wherein the second layer is a wire mesh.

5. The composite of claim 1 wherein the second layer is steel wool.

Percent thickness of composite Second Third Composite occupied by layertypc layer type thickness second layer (Table III) (Table IV) (inches)(0st.)

I M 65 28 I N 250 7. 2 G O 18 H O 120 17 J P 120 13 K Q, 90 10 L Q 12012. 5

What is claimed is: 1. A sheet-like composite which is adapted to becoldformable, and heat resistant comprising:

6. The composite of claim 1 wherein the third layer comprises apolyvinyl chloride homopolymer.

References Cited UNITED STATES PATENTS 2,217,821 10/1940 Shiner 161-4152,715,089 8/1955 Michener et a1 161115 2,742,391 4/1956 Warp 16l-218(Other references on following page) 17 18 UNITED STATES PATENTS FOREIGNPATENTS 885 808 12/1961 United Kingdom 161--253 9/1956 Noyes 16111510/1957 Degman 16143 885,444 12/1961 Umted Klngdom 161253 12/1957 Hahn161-253 2/1959 Kiernan et all 161215 5 HAROLD ANSHER, Pnmary Exammer 192 Juras 1, 13 47 W. E. HOAG, Asslstant Exammer 9/1965 Pooley 161-1615/1967 Weber 156-210 12/1967 Callum 1615 10 161-43, 72, 89, 96, 170,217, 218

